An observatory higher than the sky

If you ever go on a trip to the Yunnan Province in China, you probably don’t want to miss this Milky way. Image provided by Lijiang Observatory.

Credited by Dr. X. Y. Xin from all sky monitor

It’s a freezing January night, at 3200-meter above sea level, in southwest China. The wind sweeps across the mountaintop from east to west, reddening bare fingers in seconds. But looking at the stars above, you’ll easily forget where you are.

About 26 miles away from Lijiang, Yunnan, the Lijiang observatory is within a village called Gao Mei Gu. Gao Mei Gu means “a place higher than the sky” in the language of Naxi people, the only ethnic group in China that has maintained traditions of a matrilineal clan. While Lijiang is famous for its ancient city and tourism, Gao Mei Gu is famous for its starry sky.

It’s the same starry sky that has attracted some businessman to drive across half of the country — about 1200 miles — just for an overnight camping every winter, tent and telescope in his BMW trunk. And it’s the same starry sky that stopped a female officer during a tour, laying herself down on the ground and staring at the heaven-like view despite the coldness. Many amateur astronomers and enthusiasts were also moved to tears by the starry sky.

The same reputation circles among scientists. “If you really want to go to visit one observatory and only one in China, I highly recommend you go to the Lijiang Observatory in Yunnan,” says Ji Wang, a postdoctoral associate of astronomy at the California Technology Institute.

The Lijiang Observatory hosts the “most productive research optical telescope in China,” the observatory’s director, Jinming Bai, wrote in the preface of its 2016 annual report. The optical telescope he’s referring to is the 2.4m telescope. About 30 percent of active galactic nuclei identified in the world were viewed at this telescope, as well as 10 percent of the supernovae, according to Liang Chang, the chief optical engineer at the Observatory. The 2.4m telescope was also used to look for high-redshift quasars, important celestial bodies for studying universe’s early days and the evolution of black holes. In a 2016 Astrophysical Journalarticle surveying 75 high redshift quasars, researchers were able to find 36 of them with the 2.4m telescope.

Some special features of the 2.4m telescope make such discoveries possible. For example, the telescope is capable of creating both spectrographs and visual images. Its 2.3-ton primary mirror is made from materials with near-zero thermal expansion, and the mirror’s position can be auto-adjusted by air pressure for precise observation. On its Cassegrain focus, a fast instrument change system switches different instruments in less than 30 seconds, thus maximizing the telescope’s observation time.

When I visit the control room during a winter night researchers on shift are observing astronomical bodies that might be supernovae. These supernovae candidates are not confirmed yet, explains a PhD student as he zooms in to show the redshift of star of interest. Because they are too close to the galaxies around them, it’s impossible to tell the supernovae and the galaxies apart – not by direct imaging. The good news is that supernovae and galaxies have vastly different spectrograph presentations. So spectrographs collected by the 2.4m telescope will be used to disentangle these two groups of celestial bodies and to see if there are supernovae hiding insides their surrounding galaxies.

The perspectives of those young astronomers at the Lijiang Observatory are somewhat unique too. They conquer technical and financial difficulties with innovations, sacrificing family time and health by devoting themselves to this high altitude observatory in their 30s. Not only driven by an academic passion, they also have a sense of mission. They aspire to make China’s astronomy research abreast with the world’s best.

Recently, a 12-meter Optical/Infrared Telescope has been listed as a key project of China’s Thirteenth Five-Year Plan. The chief optical engineer, Chang, says while it’s ok for China to aim at building the next biggest telescopes, China needs more medium optical telescopes in the diameter range of 3-5 meters. It would mean lower investment and more scientific output. An 8-meter optical telescope in design, the Chinese Giant Solar Telescope, is expected to cost $90 million.

Yufeng Fan, engineer in chief of the Lijiang Observatory, agrees on the usefulness of optical telescopes with medium size. And Fan adds that the Lijiang observatory always looks forward to having more fresh blood to help with the team’s research.

As we step out of the dome, clouds from the east have covered almost all stars, and the night’s observation has to end. It’s past 11pm and our guide Yuxin Xin is still energetic. Staying up late is an old habit of astronomers observing the sky at night, Xin says. On the drive back to downtown, we talk about his work, future of astronomy and unsolved mysteries. To him, he says, it’s really amazing that the extreme big and the extreme small of the universe are actually in the same form: Planets orbiting the sun is somewhat like electrons orbiting the nucleus.

I think of the image I saw on one of the monitors in the telescope’s control room: two swirling distant galaxies in a long and slow process of merging together. Isn’t that image somewhat similar to the image of two single-celled organisms merging into a multicellular one under the microscope? Not usually familiar to us lay people, those two images are both beauties at another scale, wonders in different corners of the world.